Trump and his White House don’t argue on the merits. They attack the credibility of the institutions that come up with facts and arguments they don’t like.

They even do it preemptively. Last week, White House press secretary Sean Spicer warned that the nonpartisan Congressional Budget Office couldn’t be trusted to come up with accurate numbers about the costs and coverage of the Republican’s replacement for the Affordable Care Act.

“If you’re looking at the CBO for accuracy, you’re looking in the wrong place,” he said.

So what’s the right place? The Oval Office?

Bear in mind the director of the CBO is a Republican economist and former George W. Bush administration official who was chosen for his position by the Republican Congress in 2015.

No matter. The White House is worried about what the CBO will say about Trumpcare, so it throws the CBO under the bus before the bus arrives.

Trump couldn’t care less about the long-term consequences, but the rest of us should. For more than four decades the U.S. budget process has depended on the CBO’s analyses and forecasts. The office has gained a reputation for honesty and reliability under both Republican and Democratic appointees. Now, it’s tainted.

This has been Trump’s MO since he first met a fact he didn’t like.

When candidate Trump didn’t like the positive employment numbers from the Bureau of Labor Statistics showing the economy improving under the Obama administration, what did he do? He called the official unemployment rate “such a phony number,” “one of the biggest hoaxes in American modern politics” and “the biggest joke there is.”

It’s possible to take issue with the ways the Bureau of Labor Statistics measures unemployment, but why undermine public trust in the Bureau itself?

Of course, when February’s job numbers turned out rosy, Trump’s White House embraced the monthly employment report. But the damage has been done. The BLS looks political.

Spicer tries to wrap Trump’s institutional attacks in populist mumbo-jumbo: “I think [Trump] addressed that in his inaugural speech when he talked about shifting power outside of Washington D.C. back to the American people because for too long it’s been about stats … and it’s been about, what number are we looking at as opposed to what face are we looking at?”

Rubbish. The only way we can understand the true dimensions of the problems real people face is with data about these problems, from sources the public trusts. But if the credibility of those sources is repeatedly called into question by the president of the United States, there’s no shared truth.

When Trump disagreed with judicial findings about his original travel ban, he didn’t offer any reasons or analyses. Instead, he called the judge who issued the stay a “so-called judge” and attacked the appellate judges who upheld it as “so political” they weren’t “able to read a statement and do what’s right.”

When he blamed the intelligence agencies for the downfall of his first national security advisor, he didn’t spell out why. He just attacked them, issuing disparaging tweets with “intelligence” in quotation marks.

When polls show that he has a low approval rating, he doesn’t say he expects the rating to improve. He attacks the entire polling industry, asserting “any negative polls are fake news.”

When scientists come up with conclusion he disagrees with, he doesn’t offer other credible sources of scientific data. He attacks science.

Trump thinks climate change is a hoax. His new head of the Environmental Protection Agency asserted last week that climate change isn’t caused by human activity.

What does the Trump administration do to prove the point? Nothing. Instead, it tells EPA staffers to remove pages from the EPA’s website concerning climate change, and threatens to review all the agency’s data and publications, and cuts the budgets of all scientific research in government.

Trump’s big lies are bad enough because they subvert the truth and sow confusion. But Trump’s attacks on the institutions we rely on as sources of the truth are even more dangerous, because hey make it harder for the public to believe anything.

In a democracy, the truth is a common good. Trump is actively destroying the truth-telling institutions our democracy depends on.